Stuart Lancaster refuses to gamble on team selection for England's RBS 6 Nations opener against France, despite the dwindling opportunities to assess his options for the 2015 World Cup.

While stability reigns in the forwards, injury and form dictate that a new-look backline will be fielded in Paris on February 1, with fly-half Owen Farrell and full-back Mike Brown the only certainties to start.

Outside centre and the wings are the greatest source of debate, and the uncapped Jack Nowell and Anthony Watson could be installed out wide for the Stade de France showdown.

Only 20 matches remain until England launch their home World Cup at Twickenham on September 18 next year, and while Lancaster is ready to test those he believes are equipped for the task, he will not take any risks.

"The challenge is to get the team ready to try and win the World Cup because ultimately that's what we'll all be judged on," Lancaster said at the Six Nations launch in south west London.

"You would never approach a game against France, or any Six Nations match, as an experiment because you want to win.

"It's a results-based business. There are no friendlies in international rugby. You can't see a game as a trial. The players have to be ready.

"What you don't want to do is put a player into an environment like France away if they're not quite ready. It's not fair on the player.

"But if a player looks ready I'd rather find out about his potential to play international rugby now than being sat here in January 2015 worrying over whether they're ready with the World Cup just around the corner."

England must choose two from Nowell, Watson, Jonny May and Chris Ashton to fill the wing slots against France.With 37 caps, Ashton is by far the most experienced option available - May has only one - but Lancaster's patience with the out-of-sorts Saracen has almost been exhausted.

Billy Twelvetrees is a strong favourite to start at inside centre, acting as a playmaker, leaving Brad Barritt and the uncapped Luther Burrell to duel for the number 13 jersey.

At scrum-half any one of Ben Youngs, Lee Dickson and Danny Care, who is expected to return to training on Thursday after two weeks out with a sprained ankle, could start.

With so many question marks, Lancaster will watch training closely over the coming days before announcing his team to face France on Thursday week.

"We still have selection decisions to make in a lot of positions," said Lancaster, who revealed that tighthead prop Dan Cole missed training on Wednesday because of a sore neck and fatigue.

"We'll take a lot from how training goes this week. Thursday morning's session will be pretty full-on.

"We'll have the weekend off to think about it and then we'll select the team. We have to make that call over the next five or six days.

"You can watch as many games of rugby as you like, but I do trust my instincts on how the players come across in camp."

England have finished the last two Six Nations as runners-up, on both occasions losing to eventual winners Wales. Lancaster admits it is time to improve on that record.

"We've drawn with South Africa, beaten Australia and beaten New Zealand, so our confidence and self-belief are growing," he said.

"As with all players and teams, you want to win things. You want to win trophies and series. That's the ambition for everyone.

"It starts and ends against France - you don't start thinking about what you'll do against Italy in the fifth game or Wales in the fourth game.

"But the challenge facing us is tough because we have three games away, the first two against France and Scotland away."